The High Dispersion of Phenolic Concentration in the Seeds, Skins and Wines of Vitis vinifera L. Cultivars Limits Comparative Analysis and Varietal Categorization Under Heterogeneous Conditions

This comparative literature review evaluated the polyphenolic profiles in seeds, skins, and wines of nine Vitis vinifera L. cultivars. The data compilation revealed that total tannins and catechin exhibited comparatively more homogeneous phenolic profiles in seeds than skins, suggesting differential tissue regulation of specific phenolic biosynthetic pathways within the berry. However, this pattern did not extend to total phenols or epicatechin. Furthermore, the results confirmed wide inter- and intra-cultivar polyphenolic variations, with intra-cultivar dispersion frequently reaching a magnitude comparable to, or exceeding, that observed between cultivars. These variations are likely related to the multifactorial effect of environmental, genetic, and cultural contexts on polyphenol concentration in grapes and wines due to methodological differences (extraction protocols, various quantification techniques and winemaking practices) and biological factors (edaphic and climatic conditions). Furthermore, this high inter- and intra-cultivar variability leads to overlapping concentration ranges, preventing strict varietal categorization. This demonstrates that each study represents only a snapshot of specific environmental and agricultural conditions. Consequently, this review underscores that standardized analytical protocols, rigorous experimental designs, and robust biological replication are essential to distinguish between experimental noise and biological variability, reinforcing the value of comprehensive phenolic profiles for genotypic characterization and targeted winemaking decisions.